Fuel tank

ABSTRACT

Fuel tank comprising a canister containing a composition capable of retaining fuel vapours and which is associated with an overfill prevention device also located inside the tank.

Current tanks for liquid or gaseous fuel need to meet a collection ofsafety standards because of the highly inflammable and often toxicnature of the fuel they contain. Fuel leaks through defective sealingand losses through evaporation have been the particular subject ofincreasingly tight regulations, particularly in applications to motorvehicles. In addition to the actual tank itself, a great manyaccessories associated with it may also contain fuel, for example: theconduits, various connections, pumps, filters, canisters for removingvapours, valves and safety devices, etc. These accessories often play anot insignificant part in fuel leaks of all kinds. They are sometimeseven responsible for most losses of fuel from the overall systemcontaining them together with the tank with which they are associated.

There has therefore been a search, in parallel with the reducing of theleaks caused by the tank itself, to minimize also those caused directlyby each of these acessories and by the devices that interconnect them.

U.S. Pat. No. 4,852,761 discloses a tank equipped with a canister forretaining fuel vapours which is arranged inside the tank and comprises asafety valve preventing liquid from leaving the tank if the latter isinverted. This arrangement makes it possible to dispense with theconduit connecting the tank to the canister and to shorten the conduitconnecting the refuelling vapour recovery device to this same canister.

According to this state of the art, the canister is not, however,associated with an OP device and the risk of evaporative losses due tothe connections between this device and the canister are notinsignificant.

Furthermore, the complexity of the mounting of this canisterincorporated into the tank and of the independent OP device is stillhigh. The same is true of other devices fulfilling the other functionoften encountered in fuel systems involving the presence of a tank(ORVR, OBD, etc.).

Furthermore, in the canister described in U.S. Pat. No. 4,852,761, themaximum fuel level permitted in the tank is relatively low, given theneed not to exceed the level fixed by the position of the orificesituated at the lower end of the inclined tube internal to the canisterand intended to return the liquid fuel to the tank, otherwise theseparation of liquid fuel from vapours will be inhibited. Finally, acanister of this type may find itself immersed in the fuel if the tankis inclined at an exaggerated angle, when the valve which closes thetank off in the event of rolling-over has remained open because there isstill a resultant force, of gravity which keeps the dense part of thevalve in its lowered position. This situation may result in leaks ofliquid fuel from the tank and in the composition with which the canisteris filled ceasing its fuel-gas-retaining activity.

It is an object of the invention to overcome the drawbacks of the knowntanks by providing a tank which cancels or very greatly limits the leaksof liquid and gaseous fuel to the external atmosphere while at the sametime fulfilling the safety functions generally accomplished by modernfuel systems and very greatly simplifying the complexity of the mountingof the tank.

To this end, the invention relates to a fuel tank comprising a canistercontaining a composition capable of retaining fuel vapours, in which thecanister is associated with an overfill prevention (OP) devicepreventing the tank from being overfilled and also located, at leastpartially, inside this tank.

A “tank” is to be understood as meaning a closed chamber, of varyingshapes, generally sealed against the outside, which may be equipped withvarious internal accessories or accessories passing through the wall ofthe chamber.

The tank according to the invention may be made of any composition ormaterial compatible with the fuels and the habitual conditions of use.It may, for example, by made of a material the composition of whichcontains at least one metal or one plastic. Tanks made up of at leastone plastic are preferred.

A “plastic” is to be understood as meaning any synthetic polymericmaterial which is in the solid state under ambient conditions. Tanksmade of plastic according to the invention may be in the form ofsingle-layer or multilayer tanks. Tanks comprising one or more layers ofhigh-density polyethylene are particularly preferred.

A “fuel” is to be understood as meaning any chemical composition capableof being burnt in the presence of an oxidizing agent, generally theoxygen in the air, which can be used in a combustion engine. Fuels mayat ambient temperature be in any one of three states solid, liquid orgaseous. In vehicles, preference is generally given to fuels which areliquid or gaseous at ordinary temperature and at atmospheric pressure orhigher. Liquid fuel such as petrol and diesel are particularlypreferred.

An “engine” is to be understood as meaning any engine that converts thechemical energy contained in a fuel into mechanical energy. This may beany type of internal combustion engine, of the piston or rotary type,using liquid fuel (such as petrol, heavy oil, alcohol, etc.) or gaseousfuel (such as petroleum gas, natural gas, lean gas, hydrogen, methane,etc.). By extension, a “combustion engine” is also intended to cover oneor more electric motors powered by at least one fuel cell when this fuelcontains at least one hydrocarbon and/or an alcohol.

The canister contained in the tank according to the invention is areceptacle containing a composition, generally solid and granular,capable of retaining the fuel vapours of a gaseous stream. By way of anexample of such a composition, mention may be made of granulated activecharcoal. The canister may be made of any material or composition ofmaterials compatible with the liquid and gaseous fuels with which it isintended to come into prolonged contact under the varying temperatureand pressure conditions likely to be encountered inside fuel tanks. As apreference, the canister is at least partially made of plastic.

“Plastic” here has the same meaning as above. Thermoplastics andthermosets are particularly suitable. Thermoplastics have given goodresults.

According to the invention, the canister is contained in the tank, thatis to say it is arranged completely or partially inside the latter. As apreference, it is arranged completely inside the tank.

When it is arranged completely inside the tank, the canister may befixed to the tank by any known fixing means. Examples of possible fixingmeans are, non-limitingly: bottom, side or top wall in common with onewall of the tank, bottom, side or top wall welded to a wall of the tank,protrusion from a wall of the canister bolted onto a wall or an internalpart secured to a wall of the tank, clipping of a wall of the canisterinto one or more glideways borne by or hollowed into an interior wall ofthe tank.

When it is arranged partially inside the tank, the canister penetrates awall of the tank, for example the top wall. In this case, it ispreferably closed in a sealed way by a cover carrying the gas inletconduits containing the vapours that are to be purified and theclean-gas outlet conduits. In addition, it is advantageous for the coverto be made of at least one material which is practically impermeable tothe fuels.

According to the invention, the canister is associated with an overfillprevention device preventing the overfilling of the tank.

An “OP device” is to be understood as meaning any device whose functionis to fix the useful volume of the tank and prevent the liquid in thetank exceeding a predetermined level during the filling operation. Itmay be chosen from all known devices for fulfilling this function. Theparticular OP device with a dense ball which, by gravity, blocks off thegas outlet conduit of a capacity intended to receive liquid fuel hasgiven good results. It is of particular benefit when the fuel vapoursare discharged from the end external to the tank of the filling pipe.

The OP device according to the invention is also located, at leastpartially, inside the tank. The expression “at least partially inside”is intended here to mean arranged completely or partially inside thetank, just as was explained earlier on with reference to the canister.

Two other particular OP devices suited to the tank according to theinvention are the float-type OP device and the OP device comprising apair consisting of a dense part and a spring, the position of whichfollows the level of fuel.

The OP device is associated with the canister, that is to say itcollaborates with the latter with a view to ensuring the overall safetyof the tank with respect to the environment. This device may beassociated with the canister in various ways. It may constitute adistinct device thereof, the association resulting solely from therebeing one or more means of communication with the latter such as, forexample, a connecting conduit, an electric conductor, a mechanicallinking member or, on the other hand, may share or place in common withthe canister an essential element of the canister and/or of the OPdevice, such as a wall or an interior volume.

As a preference, the OP device shares at least one essential elementwith the canister. As a particular preference, the OP device shares atleast one common wall with the canister.

A “common wall” is to be understood as meaning a wall which is usedequally by the canister and by the OP device. This common wall mayresult from the assembly, prior to their use or after incorporation intothe tank, for example by welding or bonding, of a wall of the canisterwith a wall of the OP device. Alternatively, the common wall may alsoresult directly from manufacture, for example by the moulding of acomplex device which encompassed both the canister and the OP device.

This OP device may also be fixed to the tank in a similar way to the waydescribed above in respect of the canister. It may also, as analternative, be fixed solely to the canister by any known means. Inanother alternative, it may be fixed both to the tank and to thecanister.

In a first particular embodiment of the tank according to the invention,the canister is also associated with a liquid-vapour separating devicelocated, at least partially, inside the tank.

A “liquid-vapour separating device” is to be understood as meaning anydevice capable of retaining the liquid fuel which, by entrainment, mightaccompany a stream of gas laden with fuel vapours. Quite specifically itdenotes any device capable of retaining the droplets of liquid fuelcarried along with the gases containing fuel vapours which might leavethe tank. It may be made of any material compatible with the fuels. Aliquid-vapour separating device made of thermoplastic gives goodresults.

According to this particular embodiment of the tank according to theinvention, the canister is associated with the liquid-vapour separatingdevice.

The term “associated” here has the same meaning as the meaning explainedhereinabove in respect of the OP device.

The liquid-vapour separating device is arranged, in this embodiment, atleast partially inside the tank. The expression “at least partiallyinside” has the same meaning here as the equivalent expression alreadyexplained above in respect of the OP device.

According to a second embodiment of the tank according to the invention,the canister is associated with a device (ROV or roll-over valve) forshutting off the tank breather in the event of the tank rolling over andwhich is located, at least partially, inside the tank.

In this second embodiment, just as in all the other embodiments whichwill be mentioned below, the definitions of the terms “associated” and“at least partially inside” are still the same as those alreadyexplained hereinabove.

The ROV device has the function of avoiding liquid fuel leaks from thetank, in the event of a gradual or, by contrast, very rapid movement ofthe position of the tank away from its normal position for which it wasdesigned. One example is that of a tank secured to a moving bodyclimbing a steep slope, or alternatively an on-board tank that forms anintegral part of a system that experiences an abrupt rolling-over.

One particular case of the tank according to the invention is that ofone or other of the two embodiments described above in which the tankcomprises a liquid-vapour separating device and an ROV device. As apreference, the tank is at the same time in accordance with bothembodiments described above; in other words, the canister is associatedwith each of the two devices each of which is arranged, at leastpartially, inside the tank.

As an even greater preference, the liquid-vapour separating device issituated above the ROV device. This arrangement offers the advantage ofeasier return, simply under gravity, of the liquid retained in the firstdevice to the interior of the tank, via the valve of the ROV devicewhich is open when the tank is in the normal position.

As a most especial preference, the liquid-vapour separating device inthis particular case of the tank has at least one of the followingforms:

funnel

spiral

system of multiple walls forming a labyrinth.

The spiral and labyrinth shapes are intended to impose abrupt changes indirection on the gaseous stream, so as to cause droplets of liquid fuelto condense, coalesce and be retained.

In the case of the funnel, the liquid fuel separated from the gaseousstream is collected under gravity at the lowermost point of the funnel.It can then advantageously easily be returned to the tank.

It is advantageously possible to associate several of the formsmentioned hereinabove in one and the same separating device.

According to a third embodiment of the tank according to the invention,the canister is associated with a device for recovering fuel vapourswhile the tank is being filled (otherwise known as an ORVR or on-boardrefuelling vapour recovery device) which itself is also located, atleast partially, inside the tank.

Such an ORVR device has the function of ensuring that the environment isrespected by retaining fuel vapours emitted while the tank is beingperiodically filled. It is one of the two means generally adopted forsolving the problem of catching the vapours emitted during filling, theother being independent of the tank and consisting in equipping the fueldispensing pump of the service station with a vapour extraction system.

Any ORVR device compatible with the fuel and the conditions in the tankand which can be associated with the canister is suitable. This devicemay be made of various materials, for example those containing at leastone plastic. All types of plastic, thermoplastic or thermoset areappropriate. Thermoplastics have given good results.

Preferred ORVR devices are those which are capable of capturing all thevapours generated during the operation of filling an empty tank withfuel up to its maximum level. Such a system may, for example, beassociated with a canister comprising enough fuel-vapour-retainingmaterial to capture all the vapours generated during this operation.

According to a fourth embodiment of the tank according to the invention,the canister is associated with at least one pressure sensor of anon-board diagnostic (OBD) device which is located, at least partially,inside the tank.

On-board diagnostic systems are increasingly mounted in fuel systemscomprising a tank. Their purpose is to make it easier to test thesesystems when they are being fitted, and during use, so as to be able tomonitor their characteristics and their compliance with the varioussafety and environmental standards they are supposed to meet.

These systems are based on the collection of data supplied by a seriesof sensors arranged at precise locations in the fuel system. Inparticular, they often comprise one or more pressure sensors.

According to the invention, at least one of these pressure sensors isassociated with the canister and is located, in least in part, insidethe tank.

According to a fifth embodiment of the tank according to the invention,the canister is associated with at least one accessory located, at leastpartially, inside the tank.

An “accessory” is intended to mean any member in general through whichfuel passes or which is in contact with fuel and which fulfils aparticular function specific to the fuel system, including a function oftransporting fuel between two other members.

As a preference, according to this embodiment, the canister isassociated with at least one of the following accessories, this listbeing nonlimiting:

a fuel gauge,

an electrical connection leading to a fuel gauge,

a fuel pump,

a drainable volume for collecting liquid fuel,

an electrical connection for powering a fuel pump motor,

a fuel line leading to a device supplying a combustion engine,

a pressure gauge.

Any combination of at least two accessories may be used, there possiblybeing more than one of one same accessory.

According to a sixth embodiment of the tank according to the invention,the canister penetrates a wall of the tank via an orifice closed by acover surmounting the canister and in contact, on the inside thereof,with a chemical composition capable of retaining fuel vapours.

The cover of the canister preferably closes the orifice in a wall of thetank in such a way that it is sealed off with respect to the liquids andgases under the pressure and temperature conditions customarily found ina fuel tank.

As a preference, this cover comprises at least one plastic impermeableto hydrocarbons. A cover which has given good results is made ofimpermeable thermoplastic. Examples of such hydrocarbon-impermeableplastics are, non-limitingly, polyethylene terephthalates, polyamides,polyketones, polyacetals and multilayer structures comprising, forexample, at least one layer of high-density polyethylene and possibly abarrier layer that forms a barrier against hydrocarbons.

The closing of the orifice in the tank by the cover may be sealed by anypossible means of assembly. It may, for example, be ensured by using aseal between the cover and the tank. In the case of a cover made ofplastic and when the tank is itself also made of plastic, the tankorifice is sealed closed advantageously by welding the cover of thecanister to the wall of the tank.

The chemical composition capable of retaining the fuel vapours has thesame definition as the composition, generally solid and granular,defined above as being a composition with which the interior volume ofthe canister can be filled.

According to a seventh embodiment, one advantageous alternative formconsists in causing part of the filling pipe to enter the tank in such away as to be associated with the canister. It is thus possible for thecanister/filling pipe assembly to be preassembled by any known means sothat this assembly can be mounted in or on the tank in a singleoperation.

In the configuration where the canister lies fully inside the tank, itis also advantageous for all of the conduits and connections intended toleave the tank to be associated with the canister.

In this seventh embodiment, the term “associated” has the same meaningas described above with regard to the OP device.

When the canister is located partially outside the tank, anotheradvantageous alternative form consists in gathering together all theconduits and connections leading to the tank in the part external to thetank. Thus, the tank has no orifice other than the one intended for thecanister.

According to an eighth embodiment of the tank according to theinvention, the canister may be associated with an electrically operatedvalve of the canister bleed circuit. The term “associated” here againhas the same meaning as before,

Two or more of the particular embodiments mentioned above mayadvantageously be combined.

One preferred combination is the one in which a DVMPTOV valve isintegrated into a canister placed in a tank. The DVMPTOV valve(Drainable-Volume Multi-Purpose Tank Overfill Valve) combines the ROV,tank breather, OP and liquid-vapour separating functions.

The invention also relates to a tank like one of those describedhereinabove and intended to be mounted in a motor vehicle.

A “motor vehicle” is intended to mean vehicles propelled by a combustionengine, such as lorries, cars and motor cycles.

FIGS. 1 to 4 which follow are given with a view to illustrating, theinvention without restricting its scope.

These figures depict a plan view (FIG. 1) of a canister suited to a tankfor a motor vehicle according to the invention, and three elevations ofthe same canister corresponding to sections on the lines AA (FIG. 2), BB(FIG. 3) and CC (FIG. 4) as marked in FIG. 1.

In these figures, a cover (1) of circular shape made of PA of a canister(37) made of HDPE comprises a breather orifice (2), a bleed pipette (3)and a head of a multipurpose valve (4) with a drainable volume (11) andis welded to the wall of a tank (33) made of HDPE. This valve comprisesa dense steel ball (5) surmounted by a float (6), the ball-floatassembly lying inside a tubular part (7) in the form of a skirt in whichthe float (6) slides freely. The dense ball (5) rests on a perforatedbottom (35) in the form of an inverted truncated cone, secured to theskirt (7) and lying approximately mid-way up the latter. The skirt (7),the perforated bottom (35) and the float (6) are made of polyacetal. Apassage (36) in the top of the skirt (7) at a point located near thecover (1) provides communication between the inside of the tank (34) andthe inside of the skirt (7). The latter is fixed to the head of thevalve (4) by clipping. Surmounting the float (6) in the head of thevalve (4) is a passage (9) delimited by an elastomer seal (10) andconnecting the inside of the valve to a duct (8) lying in the head ofthe valve, above the level of the wall of the tank (33). The top of thefloat (6) has a shape capable of blocking off the passage (9) when it isin contact with the seal (10). The duct (8) opens into a cavity (11)which itself is also secured to the cover (1). At the base of the cavity(11) there is a passage (12) closed by a seal (13) in the shape of aninverted umbrella. A second cavity (14) surmounts the cavity (11) and isconnected thereto by a passage closed off by a dense steel ball (16)allowing the tank to be closed off when it is in the position of restclose to the horizontal. In close proximity to the ball (16) there is asecond passage (17) of smaller size, itself communicating with a smallcavity (18) which contains a small-sized dense ball (19). Anotherpassage (20) connects the small cavity (18) to the main cavity (11). Theupper cavity (14) is extended by the line (21) incorporated into thecover (1) and which ends in another cavity (22) located under the bleedpipette (3). This last cavity (22) surmounts a bed of active charcoalgranules (24) protected by a layer of soft gas-permeable polyurethanefoam (23). A wall (25) separates the bed of granules (24) into tworegions and leaves a space (26) between its base and the bottom of thecanister (37) to allow communication between the two regions. Alsoarranged at the top of the bed (24) are protections (23) and (27) madeof soft polyurethane foam, on each side of the wall (25). Theprotections (23) and (27) are held in place above the bed of granules(24) using metal springs just one (28) of which is illustrated forreasons of clarity. A cavity (29), symmetric with the cavity (22) islocated above the protection (27) under the breather orifice (2). Thisorifice (2) itself is composed of a pipette (30) surmounted by aprotective cap (31). The granules (24), the wall (25), thepolyurethane-foam protections (23) and (27) and the cavities (22) and(29) are contained inside a receptacle (32) made of HDPE sealedhermetically by the cover (1). The parts of the canister (37) which areexternal to the receptacle (32) and to the main cavity (11) are in freecommunication with the inside of the tank (34).

The way in which the canister described hereinabove works is as follows:when the tank is in a normal position of rest, the gaseous phase sittingon top of the liquid fuel present in the tank is in communication withthe open air via the passage (36), possibly via the space between theskirt (7) and the float (6) and via the passage (9), the duct (8), thecavity (11), the small cavity (18), the cavity (14), the line (21), thecavity (22), the bed of active charcoal (24), the cavity (29) and thepipette (30). If, for any reason, the gaseous atmosphere inside the tankexperiences a modest overpressure, and the level of liquid fuel remainsbelow a critical level situated below the level of the passage (36), thetank will be vented by exhausting some of the gases via this passage(36) and the path described hereinabove to exit in the open air, oncethe fuel vapours have been retained in the active charcoal (24). In thissituation, the float (6) remains low enough to leave the passage (9)open. If liquid fuel were to be entrained with the gaseous stream, or ifcondensation were to occur, this liquid or this condensation would beretained in the volume (11). When the level of liquid fuel retained inthe volume (11) exceeds a certain critical weight, the seal (13) opensand the liquid returns to the tank (34).

If there is an overpressure inside the tank when the level of liquidfuel exceeds a certain critical level, the float (6) rises and closesthe passage (9), it being possible for the passage (36) to be immersedunder the fuel, thus preventing large quantities of liquid from enteringthe duct (8), preventing the cavity (11) from filling, preventing thebed of active charcoal (24) from becoming immersed, and preventing fuelfrom leaking from the tank.

If the tank is accidentally rolled over, the ball (5) comes out of itshousing and, under the effect of gravity, pushes against the float (6),thus shutting off any leak of liquid from the tank.

When the motor vehicle in which the tank is mounted remains stationaryin the position close to the horizontal and the overpressure in the tankremains modest, the dense ball (15) rests on its seat and shuts off thepassage (16), while the gaseous atmosphere in the cavity (11)communicates with the duct (14) via the narrow passage (17), and ventingthen continues in the normal way as explained above.

If there is a significant overpressure in the tank, such as that whichoccurs, for example, when the tank is being filled, the pressurized gascontaining fuel vapours enters the passage (20), pushes the ball (19)which rises up in the cavity (18) and blocks off the passage (17) so asto close the tank.

If there is a depression inside the tank when the latter is stationaryin the position close to the horizontal, the ball (19) drops back downinside the cavity (18). The latter has an internal shape such that whenthe ball (19) has reached its lowermost point, the passage (20)nonetheless still remains open.

If the vehicle is in motion, the dense ball (15) leaves its seat andopens the passage (16) which allows direct communication with the cavity(14) and the line (21).

What is claimed is:
 1. A fuel tank comprising a canister containing acomposition capable of retaining fuel vapours, wherein the canister isassociated with an overfill prevention (OP) device preventing the tankfrom being overfilled above a predetermined maximum level during fillingof the tank with fuel, said OP device being located, at least partially,inside said tank and the canister further being associated with afurther device, responsive to overpressure and located, at leastpartially, inside said tank, for preventing fuel from entering saidcanister.
 2. Tank according to the preceding claim, wherein the OPdevice has at least one wall in common with the canister.
 3. Tankaccording to claim 1, wherein the canister is associated with aliquid-vapour separating device located, at least partially, inside thetank.
 4. Tank according to claim 1, wherein said further devicecomprises a device (ROV) for shutting off a tank breather in the eventof the tank rolling over.
 5. Tank according to claim 1, wherein thecanister penetrates a wall of the tank via an orifice closed by a coversurmounting the canister and in contact, on the inside thereof, with achemical composition capable of retaining fuel vapours.
 6. Tankaccording to claim 1 fitted inside a motor vehicle.